Field of the Invention
The invention lies in the automotive technology field. The invention relates to a device and a method for triggering an occupant protection system in the event of a motor vehicle rollover. The expression "motor vehicle rollover" as used herein includes both a threatened motor vehicle rollover and a rollover that is actually taking place.
Occupant protection systems that can be activated in the event of a motor vehicle rollover include, for example, passive restraint systems such as, i.e., a head airbag, a side airbag, a seat belt pretensioning system, a seat belt clamping system, and/or an upwardly foldable rollover bar. Furthermore, occupant protection can also be enhanced by using systems that can be activated during and after an accident (post-crash systems). Such systems can include, for example, generating an emergency signal, opening the central locking, switching on the hazard warning system, and/or switching off the fuel pump.
German Patent DE 35 45 874 C1, corresponding to U.S. Pat. No. 4,715,468, discloses a device triggering an occupant protection system in the event of a motor vehicle tilting movement about a motor vehicle longitudinal axis. The device includes an inertia switch that is closed when there are vehicle accelerations in the vehicle's x- and y-planes above a specific acceleration value. When the threshold is exceeded, the device activates a rollover bar occupant protection system. Connected in parallel with the inertia switch is a series circuit made of inclination switches, which detect rolling movements of the motor vehicle, and suspension switches. The rollover bar is triggered whenever one of the inclination switches responds and one of the suspension switches signals rebounding of a motor vehicle rear wheel. However, in certain circumstances, for example, extreme cornering, there is the risk of an unnecessary, surprising, and, therefore, dangerous triggering of the occupant protection system. Correct, timely triggering of the occupant protection system is not ensured in all accident situations.
European Patent 0 430 813 B1 discloses an occupant protection system including a gyrometer and three accelerometers that determine the longitudinal, transverse, and vertical accelerations of the motor vehicle. The triggering device of the occupant protection system is activated either when the combined longitudinal and transverse accelerations exceed a prescribed threshold value, when the gyrometer output signal is situated above a specific threshold, or when the gyrometer output signal integrated over a prescribed time interval exceeds a specific threshold. The gyrometer output signal is, however, not referred to a fixed space coordinate system, and, therefore, does not permit a firm conclusion on the actual angle of inclination of the motor vehicle with reference to the horizontal plane. For the system, certain is difficulties are encountered for determining the triggering threshold value.